Drip chamber for intravenous infusion

ABSTRACT

The present invention relates to a drip chamber for an intravenous infusion set. The invention also relates to a method of making drip chambers, and further, to an intravenous infusion set including a drip chamber. The invention is provided with a drip chamber comprising a housing defining a chamber to be located in a vertical position and including an inlet at the top and an outlet at the bottom; a first hydrophilic filter covering the outlet effective, when wet, to permit the flow therethrough of a liquid and to block the flow therethrough of air; and a second hydrophilic filter covering the inlet also effective, when wet, to permit the flow therethrough of a liquid and to block the flow therethrough of air.

The present invention relates to a drip chamber for an intravenousinfusion set. The invention also relates to a method of making dripchambers, and further, to an intravenous infusion set including a dripchamber.

Intravenous infusion sets commonly include drip chambers to enable theflow rate of the infusion liquid to be visually observed. It isfrequently desirable to filter the infusion liquid at the time it isadminstered to the patient. A hydrophilic filter may be used for thispurpose, as described for example in U.S. Pat. Nos. 4,013,072 and4,521,212, since such filters, when wetted with the liquid, pass liquidbut block air.

An object of the present invention is to provide a novel drip chamber ofthe type including a hydrophilic filter. Another object of the inventionis to provide an intravenous infusion set including a drip chamber and abypass arrangement to facilitate priming the infusion set. A furtherobject is to provide a method of making a drip chamber having a filter.

According to one aspect of the present invention, there is provided adrip chamber for an intravenous infusion set, comprising: a housingdefining a chamber to be located in a vertical position and including aninlet at the top and an outlet at the bottom; a first hydrophilic filtercovering the outlet effective, when wet, to permit the flow therethroughof a liquid and to block the flow therethrough of air; and a secondhydrophilic filter covering the inlet also effective, when wet, topermit the flow therethrough of a liquid and to block the flowtherethrough of air.

Such a drip chamber is particularly useful in an intravenous infusionset for home self-treatment, in order to make the set usable as easilyas possible by the user. A drip chamber including hydrophilic filters atboth its inlet and outlet enables the drip chamber to be pre-connectedinto an infusion set with the infusion bag, and to be pre-primed, so allthe patient has to do is to connect the intravenous tube to the outletend of the drip chamber and start the infusion.

Thus, during storage and handling of infusion sets including a dripchamber having a hydrophilic filter only at the outlet end, air in thedrip chamber could escape into the infusion bag, and consequently thedrip chamber could fill and become ineffective. However, by providingthe drip chamber with a hydrophilic filter at both its inlet and outletends, the infusion set may be pre-primed before being stored, in whichcase the hydrophilic filters at the two ends of the drip chamber becomewet and thereby prevent air from escaping either way, so that the dripchamber remains operational until used.

Such a construction, or one including a filter only at the outlet of thedrip chamber, may also be used for fine filtration of the infusionliquid, e.g., for filtering out microorganisms. However, the flow ratethrough the filter would be quite low, and therefore it would generallybe desirable to include an infusion pump to apply sufficient pressurefor the desired flow rates. In order to permit priming of such aninfusion set within a short time, the infusion set may be provided witha bypass for bypassing the drip chamber.

According to another aspect of the present invention, therefore, thereis provided an intravenous infusion set comprising: a housing defining achamber to be located in a vertical position and including an inlet atthe top and an outlet at the bottom; a filter covering the outlet;bypass tubing connecting the inlet to the outlet and bypassing thechamber; and a valve in the bypass tubing, which valve is normallyclosed but is manually openable to bypass the chamber when priming theinfusion set.

According to a further aspect of the present invention, there isprovided a method of making a drip chamber, comprising: producing acylindrical wall open at least at one end to constitute the bottom ofthe drip chamber; producing a bottom wall member including a circularwall integrally formed with a cylindrical skirt circumscribing thecircular wall and formed with an annular seat around the cylindricalskirt at one side of the circular wall, and with a hollow stem extendingaxially from the center of the other side of the circular wall; securinga filter to the annular seat; and bonding the bottom wall member withthe filter secured thereto to the open end of the cylindrical wall withthe filter disposed within the cylindrical wall and the hollow stemprojecting outwardly of the cylindrical wall.

According to a further preferred feature, the bottom wall member isbonded to the cylindrical wall by spin welding, i.e., by spinning onewith respect to the other to produce frictional heat sufficient to weldthe two together.

According to a further aspect of the present invention, there isprovided a method of making a filtering type drip chamber, comprising:making a drip chamber including a cylindrical wall open at one end andclosed at its opposite end by an end wall integrally formed with ahollow outlet stem; inserting through the open end a carrier membercarrying a filter; moving the carrier member to the opposite end of thedrip chamber to engage the end wall; and applying heat and pressure fromthe external side of the cylindrical wall to bond the carrier member tothe cylindrical wall.

While the foregoing features are particularly useful for making dripchambers having hydrophilic filters at both its ends, it will beappreciated that the above-described method and bypass construction canalso be used with respect to drip chambers having a single filter, e.g.,at its outlet end.

Further features and advantages of the invention will be apparent fromthe description below.

The invention is herein described, by way of example only, withreference to the accompanying drawings, wherein:

FIG. 1 is an exploded view illustrating the main components of one formof drip chamber constructed in accordance with the present invention;

FIG. 2 illustrates the drip chamber of FIG. 1 in assembled form with anintravenous infusion set including an infusion bag;

FIG. 3 is an enlarged plan view of the inner face of the bottom end wallof the drip chamber of FIG. 2 but without the hydrophilic filter;

FIG. 4 is a sectional view of the bottom end wall of FIG. 3, includingthe hydrophilic filter to be mounted thereto before it is fixed to thebottom end wall;

FIG. 5 is a view similar to that of FIG. 4 but after the hydrophilicfilter has been fixed to the bottom end wall;

FIG. 6 illustrates one manner for fixing the bottom end wall, includingthe hydrophilic filter attached thereto, to the cylindrical side wall ofthe drip chamber;

FIG. 7 illustrates one manner for fixing the hydrophilic filter at theinlet end of the drip chamber;

FIGS. 8 and 9 are plan views, corresponding to that of FIG. 3,illustrating other spacing rib configurations that may be used forspacing either or both hydrophilic filters from their respective endwalls;

FIGS. 10, 11 and 12 illustrate another method that may be used formaking a drip chamber having a filter;

FIG. 13 is a fragmentary sectional view illustrating one example of theconstruction of a drip chamber made according to the method of FIGS.10-12;

FIG. 14 illustrates an infusion set including a drip chamber, infusionpump, and a bypass tubing to facilitate priming the infusion set;

FIG. 15 is an enlarged, longitudinal-sectional view of themanually-openable valve in the bypass tubing of FIG. 14;

and FIG. 16 is an enlarged sectional view along line XVI--XVI of FIG.15.

FIG. 2 illustrates an intravenous infusion set for administering aninfusion liquid, contained with an infusion bag 2, to a patient via adrip chamber 3 provided with a spike 4 for penetrating the infusion bag.At the time of administering the infusion liquid, the infusion bag 2 issuspended above the patient, and the drip chamber 3 is supported in avertical position such that the flow rate of the infusion liquid may beobserved by the rate of formation of drops of the infusion liquid froman inlet stem 5 into the drip chamber 3 during passage at the infusionliquid through outlet stem 6 and tube 7 leading to the patient.

FIG. 1 more particularly illustrates the construction of the dripchamber 3. It includes a cylindrical side wall 10 closed at its upperend by a top wall member 11 integrally formed with the inlet or dripstem 5, and closed at its bottom with a bottom wall member 12 integrallyformed with the outlet stem 6. The inlet spike 4 is carried by an inletfitting 13 applied over the top wall member 11. A hydrophilic filtermembrane 14 is provided between the inlet fitting 13 and the top wallmember 11. Another hydrophilic filter membrane 15 is provided over thebottom wall member 12.

The drip chamber assembly illustrated in FIG. 1 further includes aprotector sleeve 16 which is normally applied over spike 4 duringnon-use or storage of the drip chamber. When the drip chamber is to beused, protector sleeve 16 is removed to enable the spike 4 to penetratethe infusion bag 2, as shown in FIG. 2.

It is desired to simplify as much as possible the use of the infusionset, e.g., for home self-treatment by the patient. For this purpose, thedrip chamber 3 may be pre-connected to the infusion bag 2 and filledwith the infusion liquid; and the set may then be pre-primed. Thus, allthe patient would have to do is to suspend the infusion bag and the dripchamber over the patient (FIG. 2), connect the outlet tube 7 to thepatient's intravenous cannula (not shown), and start the infusion.

Such an assembly could be stored for use with both hydrophilic filters14 and 15 wetted by the infusion liquid. Hydrophilic filter 14 wouldthereby permit the infusion liquid to flow into the drip chamber viainlet stem 5, but would block the flow of air in either direction.Similarly, hydrophilic filter 15 would permit the infusion liquid toflow out of the drip chamber via outlet stem 6, but would also block theflow of air in either direction. Thus, air is prevented from escapingeither way, and the drip chamber therefore remains essentially empty andoperational until used.

FIGS. 3-5 illustrate the construction of the bottom wall member 12, andparticularly the manner of securing the hydrophilic filter 15 to it.

As shown particularly in FIGS. 4 and 5, the bottom wall member 12includes a circular end wall 20 of conical configuration which closesthe bottom of the drip chamber 3 except for the outlet stem 6, and anannular wall 21 around its circumference and formed with a flat annularseat 22 for receiving the hydrophilic filter 15. Annular seat 22 iscircumscribed by an annular lip 23 rising above the upper surface of thehydrophilic filter membrane 15. The bottom wall member 12 is furtherformed with a cylindrical skirt 24 joining annular wall 21 andterminating in an outer annular rib 25 in its end opposite to thatreceiving the hydrophilic filter 15.

It will thus be seen that the outlet stem 6 is integrally formed on theouter surface of end wall 20, whereas the annular seat 22 receiving thehydrophilic filter 15 is formed on its inner surface so that thehydrophilic filter 15 will be disposed within the drip chamber 3 tooverlie the outlet stem 6. The inner surface of end wall 20 is furtherformed with a plurality of circumferentially-extending spacer ribs 26 tospace the hydrophilic filter 15 from the open end of the outlet stem 6.

The hydrophilic filter 15 may be sensitive to the solvent commonly usedin adhesives. FIGS. 4-6 illustrate a manner of securing hydrophilicfilter 15 to the the bottom wall member 12, and of securing the bottomwall member 12, together with the hydrophilic filter 15, to the bottomend of the cylindrical side wall 10 of drip chamber 3, such as tosubstantially protect the hydrophilic filter from exposure to thesolvent of the adhesive.

After the hydrophilic filter 15 has been applied to the flat annularseat 22 of the bottom wall member 12 (FIG. 4), a heated swaging die (notshown) is applied to the annular lip 23 to turn the lip over onto theouter circumference of the hydrophilic filter 15 (FIG. 5), and therebyto secure the hydrophilic filter firmly to the bottom wall member 12.The bottom wall 12, including the hydrophilic filter 15 secured to it,is then secured to the bottom end of the cylindrical side wall 10 byinserting a portion of the cylindrical skirt 24 into the respective endof side wall 10, leaving a portion of skirt 24 outside as shown at 24ain FIG. 6. An adhesive 27 is applied to skirt portion 24a, and then thebottom wall 12 is completely inserted until its annular rib 25 abutsagainst the end of the side wall 10. This procedure bonds the bottomwall member 12 to the side wall 10 in a manner which substantiallyprotects the hydrophilic filter 15 from exposure to the solvent of theadhesive.

Another preferred manner of bonding the bottom wall member 12 to theopen end of the cylindrical wall 10 would be by spin welding. Thus,after the filter 15 has been secured to the annular seat 22 of thebottom wall member 12 in the manner described above, the bottom wallmember is introduced through the open end of the cylindrical wall 10with the filter disposed within the cylindrical wall, and the hollowstem projecting outwardly of the cylindrical wall. Then, either thebottom wall member 12 or the cylindrical wall 10 is rotated with respectto the other to produce sufficient friction to weld the bottom wall tothe cylindrical wall.

The hydrophilic filter 14 at the inlet end of the drip chamber 3 may besecured in the same manner as described above. In this case, however,the hydrophilic filter 14 is secured to one end of the inlet fitting 13,rather than to the top wall member 11.

Thus, as shown in FIG. 7, the inlet fitting 13 is also formed with acircular end wall 30 adapted to be inserted into the inlet end of thedrip chamber cylindrical side wall 10 after the top wall member 11 hasbeen inserted and secured thereto. Before inlet fitting 13 is insertedinto the cylindrical side wall 10, the hydrophilic filter 14 is appliedto the flat inner seat 32 formed in the respective end of the inletfitting, and is secured thereto by turning-over a lip 33, in the samemanner as described above with respect to FIGS. 4 and 5 for fixinghydrophilic filter 15 on the flat annular seat 22. The inlet fitting 13is also formed, on the opposite side of end wall 30, with a cylindricalskirt 34 which is received within the inlet end of the cylindrical sidewall 10 of the drip chamber, and bonded to it in the same manner as thehydrophilic filter 15 is secured to the bottom end of the drip chamber,as described above with respect to FIG. 6.

Another manner of securing the hydrophilic filter 14 to the inlet end ofthe drip chamber would be to secure this filter to the top wall member11, in the same manner as described above with respect to FIGS. 4 and 5.The top wall member 11 may then be secured to the upper end of side wall10 by applying the adhesive to the inner surface of side wall 10 (e.g.,by dipping or spraying), and then inserting the top wall member 11together with the hydrophilic filter membrane 14. In such a case, thetop wall member 11 may be constructed as the bottom wall member 12,except for the annular rib 25.

FIGS. 8 and 9 illustrate other constructions that may be used for thebottom wall member 12, as well as for the respective end of the inletfitting 13, and for the top wall member 14. The constructionsillustrated in FIGS. 8 and 9 are basically the same as described above,except that the spacing ribs, shown at 26 in FIGS. 3-5, are in the formof radially-extending ribs, as shown at 38 in FIG. 8, and at 39 in FIG.9, respectively, radiating around the outlet stem 6.

FIGS. 10-12 illustrate a still further method that may be used formaking a drip chamber provided with a filter. In this method, a dripchamber of conventional construction is first produced to include acylindrical wall 50 open at one end 51, and closed at its opposite endby an end wall 52 integrally formed with a hollow outlet stem 53. Acarrier member 54 carrying a filter 55, e.g., a hydrophilic filtermembrane, is inserted through the open end 51 of the cylindrical wall 50and is moved therethrough to engage the end wall 52, as shown in FIG.11. Heat and pressure are then applied from the external side of thecylindrical wall 50 to bond the carrier member to the cylindrical wall,as shown in FIG. 12.

The construction of carrier member 54, including the manner in which thefilter 55 is carried by it, is more particularly illustrated in FIG. 13.Thus, carrier member 54 is in the configuration of a cylindrical skirtformed at one end with a flat annular seat 56 for receiving the filter55. The cylindrical skirt 54 is further formed with an annular lip 57circumscribing seat 56. After filter 55 has been placed on seat 56, theannular lip 57 is turned over to engage the outer periphery of thefilter 55 and thereby to firmly secure the filter to the outer peripheryof the carrier member.

As also seen in FIG. 13, when carrier member 54 is moved to engage endwall 52 of the drip chamber, filter 55 is spaced from that end wall by aspace 58.

Carrier member 54 may be a simple cylinder, without lip 57, withmembrane 55 sealed to one of the flat surfaces by heat and pressure orother conventional sealing methods. Alternatively, the membrane may bemolded into the carrier member.

A drip chamber including a filter at both its inlet and its outlet, oronly at its outlet, may also be used for fine filtration of the infusionliquid. For example, an 0.2 μm rated membrane-type filter may be usedfor filtering out most common microorganisms. However, an infusion setincluding such a drip chamber would have a very low flow rate ifgravity-fed.

FIG. 14 illustrates an infusion set which includes an infusion pump forthis purpose, and a special priming procedure to rid the infusion set ofair before use. Thus, the infusion set 60 illustrated in FIG. 14includes a drip chamber 61 having an inlet 62 at its upper end, anoutlet 63 at its lower end, and a membrane-type filter 64 covering theoutlet 63. Filter 64 may be of the hydrophilic type as described aboveto block air from entering the set downstream of the drip chamber, or itmay be a fine filter, such as an 0.2 μm rated membrane, for filteringout microorganisms. The infusion set illustrated in FIG. 14 furtherincludes an infusion pump 65 for applying sufficient pressure to theliquid downstream of the drip chamber 61 for the desired flow rates.

In order to faciliate priming the infusion set, it includes bypasstubing 66, 67 connecting the inlet 62 to the outlet 63 for bypassing thedrip chamber 61. The bypass includes a valve 70 which is normally closedbut which is manually openable to bypass chamber 61 when priming theinfusion set. A preferred construction for valve 70 is illustrated inFIG. 15 and 16.

Thus, valve 70 includes a cannula 71 having an axial passageway 72 fromone of the cannula but closed at the opposite end by an end wall 73. Theclosed end 74 of cannula 71 is of smaller diameter than the open end ofthe cannula and is formed with a plurality of radial bores 75 adjacentthe end wall 73 and leading from the axial passage 72 to the outersurface of the cannula. An elastomeric sleeve 76 overlies and normallycloses the radial bores 75. A plurality of outwardly-projecting ribs 77at the end wall 73 retain elastomeric sleeve 76 in place over the bores75.

Cannula 71 is further formed with an annular seat 78 for receiving tube66 leading to the inlet 62 of drip chamber 61, and with another seat 79at the opposite side, receiving tube 67 leading to the outlet 63 of thedrip chamber.

It will be seen that elastomeric sleeve 76 normally closes radial bores75, so that valve 70 normally blocks the flow of liquid through thebypass 60 from the inlet 62 to the outlet 63 of the drip chamber 61.However, when it is desired to prime the infusion set, the user squeezesthe elastomeric sleeve 76 at diametrically-opposed points, as shown inFIG. 16, between the radial bores 75. This causes the elastomeric sleeveto bulge outwardly at the locations of the radial bores, permitting theliquid to flow through the valve and therby bypass the drip chamber 61.

We claim:
 1. A drip chamber for an intravenous infusion set, comprising:a housing defining a chamber to be located in a vertical position andincluding an inlet at the top and an outlet at the bottom; a firsthydrophilic filter covering said outlet effective, when wet, to permitthe flow therethrough of a liquid and to block the flow therethrough ofair; and a second hydrophilic filter covering said inlet also effective,when wet, to permit the flow therethrough of a liquid and to block theflow therethrough of air.
 2. The drip chamber according to claim 1,wherein said outlet includes an outlet stem integrally formed in theouter face of a bottom wall of the housing; said bottom wall having aninner face formed with a flat annular seat receiving said firsthydrophilic filter, and with an annular lip around said annular seat;said annular lip being turned inwardly over the first hydrophilic filterto securely fix the first hydrophilic filter on said seat.
 3. The dripchamber according to claim 2, wherein the inner face of said bottom wallis further formed with a plurality of spacing ribs for spacing the firsthydrophilic filter from said bottom wall.
 4. The drip chamber accordingto claim 1, wherein said inlet includes an inlet fitting carrying saidsecond hydrophilic filter at one end, and a coupling member at theopposite end for coupling the fitting to an infusion liquid container.5. The drip chamber according to claim 4, wherein said one end of theinlet fitting is formed with a flat annular seat receiving said secondhydrophilic filter, and with an annular lip around said annular seat,said annular lip being turned inwardly over the second hydrophilicfilter to securely fix the second hydrophilic filter on said seat. 6.The drip chamber according to either of claim 4, wherein said couplingmember and at opposite end of the inlet fitting is a spike forpenetrating an infusion bag.
 7. The drip chamber according to claim 1,wherein said inlet includes an inlet stem integrally formed in a topwall of the housing and extending inwardly of the housing.
 8. Anintravenous infusion set including a drip chamber according to claim 1,in combination with a container for an infusion liquid connected to saidinlet of the drip chamber.
 9. An intravenous infusion set, comprising: ahousing defining a drip chamber to be located in a vertical position andincluding an inlet at the top and an outlet at the bottom; a filtercovering said outlet; bypass tubing connecting said inlet to said outletand bypassing said drip chamber; and a valve in said bypass tubing,which valve is normally closed but is manually openable to bypass saiddrip chamber when priming the infusion set.
 10. The infusion setaccording to claim 9, further including a pump for applying pressure tothe liquid in said infusion set.
 11. The infusion set according toeither of claim 9, wherein said filter is a hydrophilic filtereffective, when wet, to permit the flow therethrough of a liquid and toblock the flow therethrough of air.
 12. The infusion set according toclaim 9, wherein said outlet includes an outlet stem integrally formedin the outer face of a bottom wall of the housing; said bottom wallhaving an inner face formed with a flat annular seat receiving saidfilter, with an annular lip around said annular seat and turned inwardlyover the filter to securely fix it on said seat, and a plurality ofspacing ribs for spacing the filter from said bottom wall.
 13. A dripchamber for an intravenous infusion set, comprising: a cylindricalhousing defining a chamber to be located in a vertical position andincluding a top wall having an inlet and a bottom wall having an outlet;a hydrophilic filter covering said outlet effective, when wet, to permitthe flow therethrough of a liquid and to block the flow therethrough ofair; said bottom wall including an outlet stem integrally formed in itsouter face; said bottom wall having an inner face formed with a flatannular seat receiving said hydrophilic filter, and with an annular liparound said annular seat, said annular lip being turned inwardly overthe hydrophilic filter to securely fix the hydrophilic filter on saidseat wherein the inner face of said bottom wall is further formed with aplurality of spacing ribs for spacing the hydrophilic filter from saidbottom wall.
 14. The drip chamber according to either of claim 13,wherein said bottom wall is of circular configuration and is formed witha cylindrical skirt bonded to the cylindrical housing.
 15. A method ofmaking a drip chamber, comprising:producing a cylindrical wall open atleast at one end to constitute the bottom of the drip chamber; producinga bottom wall member including a circular wall integrally formed with acylindrical skirt circumscribing the circular wall and formed with anannular seat around the cylindrical skirt at one side of the circularwall, and with a hollow stem extending axially from the center of theother side of the circular wall; securing a filter to said annular seat;and bonding said bottom wall member with the filter secured thereto tosaid open end of said cylindrical wall with the filter disposed withinthe cylindrical wall and the hollow stem projecting outwardly of thecylindrical wall.
 16. The method according to claim 15, wherein saidbottom wall member is secured to said cylindrical wall by spin welding.17. The method according to claim 15, wherein said filter is attached tosaid annular seat by forming said annular seat with an outer annularlip, placing the filter on said annular lip, and turning over saidannular lip to attach said filter to said annular seat.
 18. A method ofmaking a filtering type drip chamber, comprising:providing a dripchamber including a cylindrical wall open at one end and closed at itsopposite end by an end wall integrally formed with a hollow outlet stem;inserting through said open end a carrier member carrying a filter;moving said carrier member to said opposite end of the drip chamber toengage said end wall; and applying heat and pressure from the externalside of the cylindrical wall to bond said carrier member to saidcylindrical wall.
 19. The method according to claim 18, wherein saidcarrier member is formed with a cylindrical skirt having one endmounting said filter, and its opposite end engageable with said end wallof the drip chamber at the time the heat and pressure are applied, tothereby space the filter from said end wall.